1. Field of the Invention
This invention relates to a process for producing a solid catalyst used in the production of olefin polymers, and more particularly to a process for producing a novel solid catalyst having a very high polymerizing activity per solid catalyst and per titanium atom which is for use in producing an olefin polymer containing very small amounts of catalyst residue and amorphous polymer and which is excellent in mechanical properties and processability.
2. Description of the Prior Art
As a process for producing polymers of .alpha.-olefins such as propylene, butene-1 and the like, the process using the so-called Ziegler-Natta catalyst constituted of a transition metal compound belonging to Group IV to Group VI of the periodic table and a organometallic compound belonging to Group I to Group III is generally well known. Particularly, in the industrial production of .alpha.-olefin polymers, titanium trichloride catalyst is widely used.
In this production process, however, amorphous polymer is formed as a by-product in addition to the valuable highly stereospecific .alpha.-olefin polymer.
This amorphous polymer is not valuable industrially and exercises a greatly adverse influence upon the mechanical properties of .alpha.-olefin polymer at the time of using it as film, fiber or other processed product.
Further, formation of the amorphous product brings about a loss in starting monomer. At the same time, it indispensably requires equipment for removing the amorphous polymer, and thereby brings about a very large industrial disadvantage.
Accordingly, if formation of such amorphous polymer can be prevented or suppressed to a slight extent, it will bring about a very great merit.
Moreover, in .alpha.-olefin polymers produced according to such a polymerization process, a catalyst residue remains to cause various troubles on stability and processability of the .alpha.-olefin polymer. Thus, it becomes necessary to provide equipment for removing the catalyst residue and stabilizing the polymer.
This fault can be overcome by enhancing the catalyst activity represented by the weight of formed .alpha.-olefin polymer per unit weight of catalyst, by which the equipment for removing a catalyst residue becomes unnecessary and the production cost of the .alpha.-olefin polymer can be reduced.
As production processes of titanium trichloride, mention may be made of the following: 1) reduction of titanium tetrachloride with hydrogen, followed by activation of the reduced product by its pulverization in ball mill, 2) reduction of titanium tetrachloride with metallic aluminum, followed by activation of the reduced product by its pulverization in ball mill, 3) reduction of titanium tetrachloride with an organoaluminum compound at a temperature of -30.degree. to 30.degree. C., followed by heat-treatment of the reduced solid product at a temperature of 120.degree. to 180.degree. C., etc.
However, titanium trichloride produced by these processes is not satisfactory in catalyst activity and stereospecificity.
In Japanese Patent Publication No. 53-3356, a process which comprises reducing titanium tetrachloride with an organoaluminum compound to obtain a reduced solid material, followed by treating the reduced solid material with a complexing agent and further reacting it with titanium tetrachloride is mentioned. Further, in Japanese Patent application Kokai (Laid-Open) No. 59-126401, a process proposed by the present inventors previously which comprises reducing a titanium compound represented by the following general formula: ##STR2## with an organoaluminum compound, followed by treating the reduced product with a mixture consisting of an ether compound and titanium tetrachloride is mentioned. If .alpha.-olefin is polymerized with a catalyst system comprising a solid catalyst component obtained according to these processes and an organoaluminum compound, however, catalyst activity is not yet satisfactorily high, though the resulting .alpha.-olefin polymer has a high stereo- specificity.
It is also known that titanium trichloride can be synthesized by reducing titanium tetrachloride with an organomagnesium compound such as Grignard reagent.
The present inventors previously proposed a process which comprises reducing titanium tetrachloride with an organomagnesium compound to obtain a solid product and treating said solid product with a Lewis acid (Japanese Patent Publication No. 57-24361) and a process which comprises reducing an alkoxytitanium compound with an organomagnesium compound in the presence of an organic silicon compound having the Si--O bond to obtain a solid product and treating said solid product with a mixture consisting of an ester compound and an ether compound (Japanese Patent Application Kokai (Laid-Open) No. 61-287904).
The catalysts obtained by these processes cannot yet give .alpha.-olefin polymer having a satisfactory stereospecificity, though they exhibit a high catalytic activity in the polymerization of .alpha.-olefins.